Shelf



FIG. 1 is a front, right, top perspective view of a shelf showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a bottom perspective view. 

CLAIM The ornamental design for a shelf, as shown and described. 